Looking at the two fill-in QBs this year, Austin Davis has a higher QBR (85.1 to Shaun Hill’s 81.3) and better completion percentage (63.4 to 59.6).
I know you were just noting that as this interesting thing and not making any kind of case. But still, this to me shows that just doing raw averages doesn’t tell you much.
So for example if you compare Davis’s 1st 3 games then his last 3, they are vastly different.
Example, using traditional qb ratings (I tend not to use QBR)…
Davis’s first 3 games … 91.3 qb rating, completion percentage 71%
Davis’s last 3 games … 60.8 qb rating, completion percentage 57.28%
Raw averages hide that difference.